This invention relates to a valve arrangement in an internal combustion engine.
Injection systems or units for fuel or air-fuel mixtures are becoming increasingly more used. Their development is particularly great in applications directed towards reducing emissions of pollutant substances, by facilitating the formation of stratified mixtures in the combustion chamber.
In view of these developments and their associated problems, cylinder head arrangements with a suitably inserted combined pump or similar device have been under development for internal combustion engines for some time. In this manner an air-fuel mixture is prepared within the combustion chamber and then directly injected into it. An example of such a cylinder head is illustrated in European patent EP-B-0514982 in the name of the present applicant.
As such a pump is of positive displacement type it is extremely important to reduce clearance volumes. In this respect, clearance volumes result in a reduction in the final pressure achieved and an insufficient change of the internal charge.
Arrangements identical to or of the same type as the aforesaid have the drawback of a certain bulk and complicated construction and assembly.
In other fields such as the field of medium-high pressure injectors for liquids, valves of a certain simplicity have been developed. These valve constructions, known as popper valves, have given little attention to the problem of bulk, seeing that they are for liquids. As clearance volumes are not a problem, these have in no respect been considered, with the result that the valve arrangements are very bulky, particularly in the valve axial direction. Consequently such arrangements cannot be used in engines, given the requirement of extreme compactness with elimination of clearance volumes.
Further problems present in the valves of current internal combustion engines are flameproofing and the ease of construction and industrial application, also in relation to the adjustment and setting of installed valves.